SiC Fibers Research Articles

Fabrication and performance of mini SiC/SiC composites with an electrophoresis-deposited BN fiber/matrix interphase

The feasibility of fabricating a BN matrix/fiber interphase of SiC/SiC composites via electrophoresis deposition (EPD) was investigated based on the simplicity and non-destructiveness of the process and the excellent interfacial modification effects of BN. The BN suspension and SiC fiber surface properties were both adjusted to generate suitable conditions for the EPD process of the BN interphase. Next, the deposition dynamics and mechanism were studied under different deposition voltages and time, and the relationship between the deposition morphology of the BN interphase and mechanical properties of the fabricated mini SiC/SiC composites were also discussed. After oxidation at high temperature (600–1000 ℃), the mechanical properties of the mini SiC/SiC composites were studied to verify the oxidation resistance effect of the EPD-deposited BN interphase, whose oxidation resistance mechanism was briefly analyzed as well.

Preparation and characterization of lightweight SiC frameworks by connecting SiC fibers with SiC joints

The increasing energy challenges and the rapidly developing astronautic technology require thermal insulators with low density and thermal conductivity, high–temperature thermal, chemical and mechanical stabilities. Herein, highly porous SiC frameworks were fabricated through procedures of assembling SiC fibers and formation of SiC joints by carbothermal reduction, which were named as SiC–bonded SiC fiber (SBSF) composites. The porosities were controlled in the range of 76–93% by varying aspect ratios of the SiC fibers. The SBSF composites exhibited outstanding corrosion resistance, oxidation resistance, and high–temperature thermal stability, as the inherent advantages of SiC ceramics. High strength and reversible compressibility were obtained in the out–of–plane compression load tests, and low thermal conductivity of 0.036–0.102 W/m · K at 25–800 °C was achieved. The results of this study suggest that the SBSF composites are a good candidate for high–temperature thermal insulators.

Effects of wet oxidation on residual stress variation of SiCf/SiC composites

Continuous silicon carbide fiber-reinforced silicon carbide matrix (SiCf/SiC) composites, used as thermal structures for gas turbines, are prone to degrade under the gas stream (mainly composed of O2 and H2O). Here, the degradation of the composites in wet oxygen environment was investigated by Raman spectroscopy. Results show that the composites exhibit significant residual stress as the oxidation proceeds. SiC matrix in the as-received condition exhibits average hydrostatic tensile stresses of approximately 1350 MPa, while SiC fiber exhibits compression stress of approximately 1450 MPa. Both the residual stresses in matrix and fiber decrease with the increasing oxidation temperature. Moreover, the residual stress evolution is found to be related to the formation of cristobalite and the volatilization of Si(OH)4, CO, H2. This work can open new alternatives for understanding the degradation mechanism of SiCf/SiC composites in gas turbine environment, and for developing mathematical model to predict their service life.

Damping Behavior of an Al-Cu Alloy Strengthened with Sic Fibers

Damping Behavior of an Al-Cu Alloy Strengthened with Sic Fibers

Impedance matching optimization of SiCf/Si3N4–SiOC composites for excellent microwave absorption properties

SiC fiber reinforced ceramic matrix composites (SiC f -CMCs) are considered to be one of the most promising materials in the electromagnetic (EM) stealth of aero-engines, which is expected to achieve strong absorption and broad-band performance. Multiscale structural design was applied to SiC f /Si 3 N 4 –SiOC composites by construction of micro/nanoscale heterogeneous interfaces and macro double-layer impedance matching structure. SiC f /Si 3 N 4 –SiOC composites were fabricated by using SiC fibers with different conductivities and SiOC–Si 3 N 4 matrices with gradient impedance structures to improve impedance matching effectively. Owing to its unique structure, SiC f /Si 3 N 4 –SiOC composites (A3-composites) achieved excellent EM wave absorption performance with a minimum reflection coefficient (RC min ) of −25.1 dB at 2.45 mm and an effective absorption bandwidth (EAB) of 4.0 GHz at 2.85 mm in X-band. Moreover, double-layer SiC f /Si 3 N 4 –SiOC with an improved impedance matching structure obtained an RC min of −56.9 dB and an EAB of 4.2 GHz at 3.00 mm, which means it can absorb more than 90% of the EM waves in the whole X-band. The RC is less than −8 dB at 2.6–2.8 mm from RT to 600 °C in the whole X-band, displaying excellent high-temperature absorption performance. The results provide a new design opinion for broad-band EM absorbing SiC f -CMCs at high temperatures.

In-situ synthesis of ternary layered Y3Si2C2 ceramic on silicon carbide fiber for enhanced electromagnetic wave absorption

A novel ternary layered ceramic of Y 3 Si 2 C 2 was successfully in-situ synthesized on the surface of home-made third-generation KD-SA SiC fiber for the first time by molten salt method aimed at improving the electromagnetic wave (EMW) absorption. After in-situ synthesis of Y 3 Si 2 C 2 ceramic layer on SiC fiber (SiC f /Y 3 Si 2 C 2 ), significantly improved EMW absorption performance was obtained. The minimum reflection loss (RL min ) of −16.97 dB was reached in SiC f /Y 3 Si 2 C 2 composites at the thickness of only 2.19 mm, and the effective absorption bandwidth (EAB) was up to 5.44 GHz (12.56–18 GHz) at a thin thickness of 2.64 mm. The improvement in EMW absorption of SiC f /Y 3 Si 2 C 2 is mainly attributed to enhanced dielectric loss and conduction loss resulting from increased heterogeneous interfaces and multiple reflections and scattering originating from net structure. The SiC f /Y 3 Si 2 C 2 could be a promising EMW absorber for application in high-performance EMW absorbing materials.

Effect of Sintering Temperature on Properties of Sic Fiber Reinforced Tungsten Matrix Composites

Effect of Sintering Temperature on Properties of Sic Fiber Reinforced Tungsten Matrix Composites

Influence of pyrolysis and melt infiltration temperatures on the mechanical properties of SiCf/SiC composites

In order to improve the degree of matrix densification of SiC f /SiC composites based on liquid silicon infiltration (LSI) process, the microstructure and mechanical properties of composites according to various pyrolysis temperatures and melt infiltration temperatures were investigated. Comparing the microstructures of SiC f /C carbon preform by a one-step pyrolysis process at 600 °C and two-step pyrolysis process at 600 and 1600 °C, the width of the crack and microcrack formation between the fibers and matrix in the fiber bundle increased during the two-step pyrolysis process. For each pyrolysis process, the density, porosity, and flexural strength of the SiC f /SiC composites manufactured by the LSI process at 1450–1550 °C were measured to evaluate the degree of matrix densification and mechanical properties. As a result, the SiC f /SiC composite that was fabricated by the two-step pyrolysis process and LSI process showed an 18% increase in density, 16%p decrease in porosity, and 150% increase in flexural strength on average compared to the composite fabricated by the one-step pyrolysis process. In addition, among the SiC f /SiC specimens fabricated by the LSI process after the same two-step pyrolysis process, the specimen that underwent the LSI process at 1500 °C showed 30% higher flexural strength on average than those at 1450 or 1550 °C. Furthermore, under the same pyrolysis temperature, the mechanical strength of SiC f /SiC specimens in which the LSI process was performed at 1500 °C was higher than that of the 1550 °C although both porosity and density were almost similar. This is because the mechanical properties of the Tyranno-S grade SiC fibers degraded rapidly with increasing LSI process temperature.

Hierarchical Sic Fiber Aerogel Toward Microwave Absorption and Thermal Insulation Application

Hierarchical Sic Fiber Aerogel Toward Microwave Absorption and Thermal Insulation Application

A Novel Two-Stage Strengthening and Toughening Behavior of Sic Fiber Reinforced Porous Ti-Nb Based Smas Composites

A Novel Two-Stage Strengthening and Toughening Behavior of Sic Fiber Reinforced Porous Ti-Nb Based Smas Composites

Etching of SiC–SiC-composites by a laser-induced plasma in a reactive gas

The precise machining of silicon carbide composite (SiC–SiC) as a high-tech material with extraordinary characteristics is required for different applications in aerospace, light weight construction and car industry. Laser machining enable new approaches for fabrication processes but the regularly applied ablation processes can cause damage to the SiC–SiC material. Here we propose and demonstrate a new approach for gentle SiC–SiC machining making use of a laser-induced plasma for reactive species generation enabling chemical material removal processes. A fs-laser (775 nm, 150 fs, 1 kHz) was focussed to a CF 4 /O 2 gas mixture igniting a laser-induced plasma (LIP) approximately 100 μm in front of a SiC–SiC sample. This LIP initiate material removal processes of the textured, multiphase SiC–SiC sample without a mechanical damage of the SiC–SiC composite structure. Different surface features such as etching of the cover SiC layer, etching of the SiC matrix and exposure, thinning and sharpen of the SiC fibres, underetching of the fibres has been observed. Across the whole etched area, no mechanical damage such as cracks, delamination's, broken fibres were observed so that a gentle machining process can be expected. • Etching of superhard SiC–SiC by a reactive, laser-induced plasma (LIP) was achieved. • Preferential etching of the matrix causes the exposure of fibres due to processing. • Selective etching of the various SiC–SiC phases causes specific surface morphologies. • Damage-free machining of the SiC–SiC composites by lasers is shown.

Mechanical Properties and Microstructural Evolution of Cansas-Iii Sic Fibers after Thermal Exposure in Different Atmospheres

Mechanical Properties and Microstructural Evolution of Cansas-Iii Sic Fibers after Thermal Exposure in Different Atmospheres

Effect of processing technology on structural stability of SiC/SiBCZr ceramic matrix composites

SiC/SiBCZr composites were prepared through polymer impregnation and pyrolysis process using the second generation SiC fibers as raw material. The effects of surface substrate removal, secondary densification, and deposition coating on the structure, mechanical properties, and high temperature stability of SiC/SiBCZr composites were investigated. Results showed that the porosity of SiC/SiC composites could be greatly diminished by the optimized treatment process, and the surface of SiC/SiBCZr composites is uniformly filled into the pores by β-SiC particles, thereby achieving the sealing effect. Meanwhile, the as-prepared SiC/SiBCZr composites had excellent high temperature structural stability. At the later stage of oxidation reaction, borosilicate oxidation products with moderate fluidity, fluid lava form and self repairing function generated from ceramic matrix can effectively inhibit the oxidation reaction and improve the high temperature structural stability of SiC/SiBCZr composites. The above-mentioned high temperature structural stability provided the foundation and technical support for improving the service life and expanding the application of SiC/SiBCZr composites.

3D printing of fibre-reinforced ceramic composites with hierarchical structure

ABSTRACT This paper reports the 3D printing of fibre-reinforced ceramic composite with hierarchical structures. Through printing precursor formulation, short SiC fibres have been successfully incorporated into silicate materials and gradient porous hierarchical structure has been achieved for the printed parts. The mechanical testing shows a 27% improvement in impact strength, 22% improvement in flexural modulus, and 7.5% in flexural strength compared with parts without fibre reinforcement. High-resolution tomography analysis using x-ray microscopy shows that the inner structure has a porosity of 27%, while the outer layer shows a dense structure with little pores formation. This 3D printed ceramic composite with fibre-reinforcement shows high similarity to the gradient porous structures of human bone and tooth. The results indicate that 3D printing of nano/microfibre reinforced ceramic composite with hierarchical structure is a promising method to enhance the fracture toughness of ceramics and allow accurate patient-specific customisation for their implants.

Novel nanometer alumina-silica insulation board with ultra-low thermal conductivity

Advanced nano-porous super thermal insulation materials are widely used in spacecraft, soler-thermal shielding, heat exchangers, photocatalytic carriers due to their low thermal conductivity. In this work, adopting dry preparation technology, nano-Al2O3, nano-SiO2, SiC and glass fibers as raw materials, novel nanometer alumina-silica insulation board (NAIB) were prepared. The preparation process was simple, safe, and reliable. In addition, the NAIB exhibited a high porosity (91.3–92.3%), small pore size (39.83–44.15 nm), low bulk density (0.22–0.26 g/cm3), better volumetric stability, and low thermal conductivity (0.031–0.050 W/(m·K) (200–800 °C)), respectively. The as-prepared NAIB could render them suitable for application as high-temperature thermal insulation materials.

Flexible ultrafine nearly stoichiometric polycrystalline SiC fibers with excellent oxidation resistance and superior thermal stability up to 1900 °C

Flexible ultrafine SiC fibers with superior high-temperature stability and excellent oxidation resistance are regarded as one of the most promising materials for high-temperature applications. However, excess oxygen and carbon in the ultrafine SiC fibers limit their thermal stability due to decomposition of the SiCxOy phase. In the present work, flexible ultrafine nearly stoichiometric polycrystalline SiC fibers were fabricated by combining the electrospinning technique and polymer-derived ceramic method. The ultrafine SiC fibers exhibited superior high-temperature stability and oxidation resistance. The retention rates of tensile strength were 90.0 %, 94.2 % and 86.4 % after heat treatment in argon at 1800 °C, 1900 °C and 2000 °C, respectively. TG results of the fibers showed little weight loss of only 1.52 % at 1900 °C in Ar and the weight gain of only 4.1 % up to 1500 °C in air. Such improved thermal stability was achieved through sintering at high temperature for elimination of excess oxygen and carbon with Al doped as the sintering aid to restrain the grain coarsening. The ultrafine SiC fibers still exhibited excellent flexibility without obvious damage when they were heated by the butane blowtorch flame of about 1100 °C in air. Furthermore, the infrared thermography illustrated that the ultrafine SiC fiber membrane also had good thermal insulation performance. The outstanding mechanical properties and thermal stability of ultrafine SiC fibers suggest their potential applications at the high temperature and harsh environment.

Gradient FeNi-SiO2 films on SiC fiber for enhanced microwave absorption performance

The microwave absorbing ability of long fibers could be effectively improved by a multi-layered coating composed of a magnetic metal and a dielectric ceramic. In this work, a gradient FeNi-SiO2 film has been deposited on SiCf (SiCf/ FeNi-SiO2) by a magnetron sputtering method. The phase composition, microstructure, and electromagnetic properties of SiCf/FeNi-SiO2 were systematically investigated. Then, the SiCf/FeNi-SiO2 was mixed with wax to study the microwave absorbing property. With only 10 wt%, the SiCf/FeNi-SiO2/wax composite exhibits excellent microwave absorption performance. The optimized reflection loss of SiCf/FeNi-SiO2 was up to -55.2 dB at 10.37 GHz with a thickness of 2.5 mm, and the absorption bandwidth below -10 dB is 6.84 GHz (from 11.08 to 17.92 GHz) with a sample thickness of only 2.0 mm. The enhanced microwave absorption performance of SiCf/FeNi-SiO2 benefits from the gradient FeNi-SiO2 film, which increases Debye dipole polarization and endows the SiCf with better impedance matching. This method can be applied to other fibers for high-performance microwave absorption.

In-situ formation of Ti3SiC2 interphase in SiCf/SiC composites by molten salt synthesis

Titanium silicon carbide (Ti3SiC2) film was synthesized by molten salt synthesis route of titanium and silicon powder based on polymer-derived SiC fibre substrate. The pre-deposited pyrolytic carbon (PyC) coating on the fibre was utilized as the template and a reactant for Ti3SiC2 film. The morphology, microstructure and composition of the film product were characterized. Two Ti3SiC2 layers form the whole film, where the Ti3SiC2 grains have different features. The synthesis mechanism has been discussed from the thickness of PyC and the batching ratio of mixed powder respectively. Finally, the obtained Ti3SiC2 film was utilized as interphase to prepare the SiC fibre reinforced SiC matrix composites (SiCf/Ti3SiC2/SiC composites). The flexural strength (σF) and fracture toughness (KIC) of the SiCf/Ti3SiC2/SiC composite is 460 ± 20 MPa and 16.8 ± 2.4 MPa∙m1/2 respectively.

Tuning SiC nanowires interphase to improve the mechanical and electromagnetic wave absorption properties of SiCf/SiCnw/Si3N4 composites

The interphase of composites is a vital element in controlling the overall performance. Herein, the SiC nanowires (SiCnw) were grown on the interface of the SiC fiber (SiCf)/Si3N4 composites and successfully achieved the integration of enhanced mechanical and electromagnetic wave (EMW) absorption performance. The introduction of SiCnw made the bonding between the SiCf and Si3N4 matrix more appropriate, thereby enhancing the mechanical properties. The defects, stacking faults, twin boundaries and heterogeneous interfaces in SiCnw improved the dielectric loss of the composites, which was beneficial to the consumption of EMW energy. Notably, the SiCf/SiCnw/Si3N4 composite containing 1.8 vol% SiCnw demonstrated the optimal mechanical and EMW absorption properties, reaching a flexural strength of 333 ± 29 MPa, a minimum reflection coefficient (RCmin) value of − 51.4 dB with a thickness of 3.2 mm and an effective absorption bandwidth (EAB) of 3.5 GHz with a thickness of 2.8 mm. Besides, the fracture mechanism and EMW absorption mechanism are also discussed. This work provides a potential new way to prepare lightweight, stable, and high-performance EMW absorbing materials for aviation and aerospace.

Edge chipping characteristics in grinding SiCf/SiC composite

Silicon carbide fiber-reinforced silicon carbide ceramic matrix composite (SiCf/SiC) is promising for manufacturing aero-engines because of its high-temperature resistance and lightweight. However, since SiCf/SiC is hard and brittle, the machining of SiCf/SiC has been suffering from uncontrolled machining-induced damages, such as edge chipping, cracks, fiber breakage. This paper studies the edge chipping characteristics of SiCf/SiC in brittle removal mode in single grain grinding. It is found that the edge chipping in grinding SiCf/SiC is complicated. The edge chipping in grinding the SiC matrix is dependent on the pre-existed defects rather than grinding parameters. While the edge chipping in grinding SiC fibers is dependent on both fiber orientation and grinding speed. The edge chipping in the grinding perpendicular to the fiber orientation is larger than that in the grinding along with the fiber orientation. It decreases with increasing grinding speed. Increasing grinding speed from 20 m/s to 50 m/s and 90 m/s, the width of the edge chipping area decreases by 30% and 60% respectively. While in the grinding along with the fiber orientation, edge chipping is minor and insensitive to grinding speed. Therefore, this study represents that increasing grinding speed would not enlarge the edge chipping but greatly increase the material removal rate, which is important for the surface finish and damage control of the machining of SiCf/SiC.